The basic input and output system (BIOS) typically controls the start-up process of a computer system. In so doing, the BIOS may perform a number of functions, including identifying, testing, and initializing system devices, such as man-machine interfaces, network interfaces, disk drives, and the like. After initialization, the BIOS may start an operating system and may pass part or all of the functions to the operating system.
The BIOS is typically stored on a read-only memory (ROM) chip. The chip may be rewritable to allow upgrading of the BIOS over the life of the computer system. For example, the chip may be an EEPROM (electrically erasable ROM) or flash memory whose contents may be updated in a process called flashing. This may be performed using a BIOS update package, which is a software product that may, for example, be provided on a flash drive, a disk, or from a remote storage system over a network connection.
Because the BIOS is often the first code that operates during startup of the computer system, it provides a potential point of attack for persons wishing to compromise the security of the computer system. Moreover, the process of updating the BIOS is often used by hackers as a way to compromise the security of a computer system. By replacing the true system BIOS with a compromised version, system security features may be disabled or not initiated in the first place.